Abstract: Objective To discuss the diagnosis and treatment of idiopathic hypereosinophilic syndrome (IHES) in children. Method The course and treatment process of a 6-year-old child with IHES had been retrospectively analyzed. Result The boy was admitted for abdominal discomfort and poor appetite, quickly developed into abdominal distension, dyspnea, jaundice, edema, and worsen hepatosplenomegaly. Routine blood test showed that the eosinophilia was 186.39×109/L. Bone marrow smear showed that the mature eosinophilcell granulocyles significantly increased to 90.4%. The FIL1P1-PDGFRα fusion gene detection, parasites and antibodies tests were all negative. CT and other examinations indicated that the digestion, circulation, blood and nervous system were all affected. The diagnosis of IHES was considered. Hydroxycarbamide and steroids applied, the eosinophil decrease, however, the symptoms no relief, eventually developed to the multiple organ failure. Conclusion IHES is rare in children. Further studies are necessary regarding the treatment and prognosis.